"We want to reinforce a lot of the stuff we started to tip off," Jon said. "'The Avengers' is a much larger concern for Marvel and Kevin Feige, who runs Marvel. They're going to be doing 'Thor' and 'Captain America,' and the way we might start to tease those things in ['Iron Man 2'], some of it is stuff that we've discussed [and] some of the stuff you do last-minute as you figure out how that stuff is coming together."

He's hoping the details will stay top-secret – though as he discovered with "Iron Man" and its secret Nick Fury (Samuel L. Jackson) cameo, it's difficult to keep things off the Internet for long.

"It's an evolving, amorphous thing. If we decide and commit too early, the secret always gets out," he said. ""As soon as we shot the Nick Fury thing — we had a closed set and nobody was supposed to know about it — week later somehow it was all over the internet. It's a little bit of a cat-and-mouse game."